By the late 1970s those minimums had really increased. When around 1979 Tsuburaya Productions hired me to write a treatment and then screenplay for their (alas, never made) American Ultraman movie, they paid me in increments according to WGA rules, and might have paid me the minimum. But what they paid for just the treatment was many times over what Bradbury got for ICFOS -- and my treatment was standard length (I'd have to dig it out, if I still had it, but it was probably around 25 to 30 pages).